Exploring the properties of Ag5–TiO2 interfaces: stable surface polarons formation, UV-Vis optical response, and CO2 photoactivation

Using a combination of first-principles modelling, X-ray absorption spectroscopy, and diffuse reflectance spectroscopy measurements, we explore the properties of Ag5–modified TiO2 surfaces. It is revealed theoretically and cofirmed experimentally a general electron polarization phenomenonassociatedwithsurfacepolaronsonTiO2. First, theAg5 clusterdonatesanelectron to TiO2, leading to the formation of polaronic Ti3+ 3d1 states on the rutile TiO2(110) surface. The analysis of polarization effects in the nearby electronic structure accompanying the polarons formation is confirmed with X-ray absorption spectroscopy measurements at the Ti K-edge of TiO2 nanoparticles. Next, the UV-Vis optical absorption spectrum of the polaronic state is also computationally modelled and an enlargement of the polaron wavefunction is predicted. Moreover, we find an overall improvement of the UV-Vis optical response of the material through diffuse reflectance spectroscopy measurements. Finally, we predict that charge-transfer processes in the Ag5–TiO2 interface triggered by solar photons might allow for a photoinduced activation of CO2 by sunlight